[MPlayer-users] Re: x264 vs xvid

[Matthias Wieser]

Am Sonntag, 27. November 2005 04:53 schrieb Dark Shadow:
> I have heard that the h264 codec is supposed to be better then regular
> mpeg4 like xvid and was wondering how much smaller would a x264 video
> would be to get the exact same quality as those 42min 350mb xvid tv
> shows that could be downloaded off the internet plus compared to a dvd
> compliant mpeg2 file with say a 2 pass 3000 bitrate.
>
> I am not good enough to do the tests and get decent results which is
> why I am asking.

In the TOOLS directory of mplayer there is a script named psnr-video.sh.

You can use it do compare different reencoded videos to the original 
video. It outputs a PSNR value which describes the mathematical 
differences between the original frames and the recompressed frames. A 
high PSNR means good quality. You should use short test videos because 
this script needs much temporary disk space. 

What you could do is:
1. Recompress a short test video with xvid (and your standard encoding
   options).
2. Calculate the PSNR between the original and the xvid file (maybe add
   "-vf pp=de" to the psnr-video.sh options if you normally use
   postpocessing during video playback). Write down the PSNR value.
3. Now recompress the test video with x264 and calculate the PSNR between
   original and the x264 file. Compare the x264 PSNR to the xvid
   PSNR. Adjust the x264 bitrate and reencode new x264 files until the
   x264 PSNR matches the xvid PSNR.
4. Compare the filesizes of the xvid file and the x264 file which has the
   same PSNR as the xvid file.

Regards,
  Matthias